Yesterday, we learned that Windows 8.1 Update 1 had hit RTM Escrow, which means development has stopped and finalizing has begun. Everything is now in place for Update 1 and no new features are set to be added.
It appears that this RTM Escrow build, (9600.16610) has apparently leaked today. Appearing as KB2919355 and KB2919442 MSU files, Update 1 requires that you perform an update to a fresh Windows 8.1 RTM install with all applicable updates applied.
At the moment, the leak pertains to x86 and x64. There will likely be a separate update for ARM platforms. Update 1 for Windows 8.1 features a host of minor tweaks and improvements, including updated taskbar functionality, Modern UI changes and much more.
We wont be providing download links to the leaked update, but you can take a look at our hands-on video here. We'll have a video of the new build up when we are able to get our hands on it!